The first thing you should know is that Beret is that she is not a floppy hat typically warn while carrying a baguette through Paris. The second thing you should know about Beret is that she never wanted to leave her parents in Norway. But once she got pregnant (which was a huge no-no back in those days) she felt like she had to marry Per Hansa and go wherever he went.
And now she's super-unhappy. Beret has zero interest in settling the American prairies. Once she actually reaches these wide-open spaces, she becomes downright terrified at how vast the land is. As the narrator tells us,
How will human beings be able to endure this place? she thought. Why, there isn't even a thing that one can hide behind! (18.104.22.168)
This fear of open spaces is technically known as agoraphobia and it pretty much defines Beret's early development as a character in this book. She might not know she has this phobia because she's probably never been in such a huge open space before. And like any frightened person, her first instinct is to run back the way she came:
Far away she had fled, from the rising of the sun to the going down thereof… so it had seemed to her… but the arm of His might had reached farther still. No, she could not escape—this was her retribution. (22.214.171.124)
Once she realizes that she's trapped out in the vastness of North Dakota, Beret feels certain that her husband has defied God by moving to this new place. That makes Beret guilty by association, and she spends much of this book worrying about what is happening to her soul and the souls of her family.
Even while Beret privately suffers, she does everything she can to give her family its best chance of survival on the desolate prairies:
[She] had let the child roam around and play in the grass while she herself had joined in their labour; she had pitched in beside them and taken her full term like any man. (126.96.36.199)
Say what you will about Beret, but she's no slouch. After all, Beret figures that she has made a commitment to Per Hansa and that she must see it through. Still, she can't help but feel as though she's holding her husband back, even as she stays devoted to him. As the narrator says,
She had bound herself inseparably to this man; now she was but a hindrance to him, like chains around his feet. (188.8.131.52)
This guilt lasts through the entire middle section of the novel. But it eventually disappears when Beret decides once and for all that Hansa has doomed himself and everyone around him to burn in hell…
Eventually, living on the prairie with nothing to do and no one to talk to causes Beret to have a mental breakdown. The only way she can recover from this episode is to glue her mind back together using the only resource she has: the old Norwegian Bible she brought with her to Dakota.
From this point on, there's nothing that happens in Beret's life that she doesn't interpret as a sign from God. After she survives her childbirth, for example, she becomes certain that she's living on borrowed time:
Ah, well, God Almighty had spared her again; He must have some reason for it… Now she could repent of her sins before He took her… He had been merciful enough to give her time for that… But sitting here in this mood, she found it impossible to repent. (184.108.40.206)
It's true that the birth of her fourth child happens before Beret's major breakdown, and you can see it in the way she is unable to repent for her previous sins. By the end of the book, though, Beret seems to do nothing but repent. After the locusts have visited her family's farm, she shouts,
"This is the work of the devil […] Now he will surely take my little boy!... God save us—we perish!" (220.127.116.11)
Beret is convinced that Satan has infiltrated her entire settlement and she ultimately sends her husband Per to his doom because she's willing to risk his life to bring a minister to see their friend, Hans Olsa. It's easy to blame Per Hansa's death on Beret's religious fervor. But the truth is that it takes two to tango, and Hansa is every bit as responsible for going on the trip as Beret is for telling him to.